Implement LookupExtractor.close() and avoid deleting off-heap cache while LookupExtractor is in use

[leventov]

Addressing https://github.com/druid-io/druid/blob/78159d7ca442cf8d99ea356d39932ab3adb8e10f/extensions-core/lookups-cached-global/src/main/java/io/druid/server/lookup/namespace/cache/OffHeapNamespaceExtractionCacheManager.java#L122

Proposed solution: make LookupExtractor closeable, and remove the cache only after it is replaced by a newer cache via periodic updates, and there are no open LookupExtractors accessing this cache. (Implementation may require some kind of manual reference counting.)

Currently, because of #3663, while off-heap cache is not functional, so this issue is not important because "closing" on-heap cache while using it is harmless ("closing" is just cleaning references to it, the cache itself is unchanged.)

[drcrallen]

One reason this was not resolved in the initial release was I couldn't find the right "responsibility chain" to tie the closeable resource into. Essentially things that require closeable resources tend to have their own QueryRunner that closes the resources appropriately, and I didn't want to add yet another one without some significant thought regarding the best way to actually handle query resources.

[stale]

This issue has been marked as stale due to 280 days of inactivity. It will be closed in 2 weeks if no further activity occurs. If this issue is still relevant, please simply write any comment. Even if closed, you can still revive the issue at any time or discuss it on the [email protected] list. Thank you for your contributions.

[stale]

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[github-actions]

This issue has been marked as stale due to 280 days of inactivity.
It will be closed in 4 weeks if no further activity occurs. If this issue is still
relevant, please simply write any comment. Even if closed, you can still revive the
issue at any time or discuss it on the [email protected] list.
Thank you for your contributions.

[github-actions]

This issue has been closed due to lack of activity. If you think that
is incorrect, or the issue requires additional review, you can revive the issue at
any time.